freebsd-skq/sys/kern/kern_fork.c
Konstantin Belousov d8b0556c6d Adapt vfs kqfilter to the shared vnode lock used by zfs write vop. Use
vnode interlock to protect the knote fields [1]. The locking assumes
that shared vnode lock is held, thus we get exclusive access to knote
either by exclusive vnode lock protection, or by shared vnode lock +
vnode interlock.

Do not use kl_locked() method to assert either lock ownership or the
fact that curthread does not own the lock. For shared locks, ownership
is not recorded, e.g. VOP_ISLOCKED can return LK_SHARED for the shared
lock not owned by curthread, causing false positives in kqueue subsystem
assertions about knlist lock.

Remove kl_locked method from knlist lock vector, and add two separate
assertion methods kl_assert_locked and kl_assert_unlocked, that are
supposed to use proper asserts. Change knlist_init accordingly.

Add convenience function knlist_init_mtx to reduce number of arguments
for typical knlist initialization.

Submitted by:	jhb [1]
Noted by:	jhb [2]
Reviewed by:	jhb
Tested by:	rnoland
2009-06-10 20:59:32 +00:00

863 lines
21 KiB
C

/*-
* Copyright (c) 1982, 1986, 1989, 1991, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)kern_fork.c 8.6 (Berkeley) 4/8/94
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_kdtrace.h"
#include "opt_ktrace.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/eventhandler.h>
#include <sys/filedesc.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/sysctl.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/pioctl.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/syscall.h>
#include <sys/vmmeter.h>
#include <sys/vnode.h>
#include <sys/acct.h>
#include <sys/ktr.h>
#include <sys/ktrace.h>
#include <sys/unistd.h>
#include <sys/sdt.h>
#include <sys/sx.h>
#include <sys/signalvar.h>
#include <sys/vimage.h>
#include <security/audit/audit.h>
#include <security/mac/mac_framework.h>
#include <vm/vm.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>
#ifdef KDTRACE_HOOKS
#include <sys/dtrace_bsd.h>
dtrace_fork_func_t dtrace_fasttrap_fork;
#endif
SDT_PROVIDER_DECLARE(proc);
SDT_PROBE_DEFINE(proc, kernel, , create);
SDT_PROBE_ARGTYPE(proc, kernel, , create, 0, "struct proc *");
SDT_PROBE_ARGTYPE(proc, kernel, , create, 1, "struct proc *");
SDT_PROBE_ARGTYPE(proc, kernel, , create, 2, "int");
#ifndef _SYS_SYSPROTO_H_
struct fork_args {
int dummy;
};
#endif
/* ARGSUSED */
int
fork(td, uap)
struct thread *td;
struct fork_args *uap;
{
int error;
struct proc *p2;
error = fork1(td, RFFDG | RFPROC, 0, &p2);
if (error == 0) {
td->td_retval[0] = p2->p_pid;
td->td_retval[1] = 0;
}
return (error);
}
/* ARGSUSED */
int
vfork(td, uap)
struct thread *td;
struct vfork_args *uap;
{
int error, flags;
struct proc *p2;
#ifdef XEN
flags = RFFDG | RFPROC; /* validate that this is still an issue */
#else
flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
#endif
error = fork1(td, flags, 0, &p2);
if (error == 0) {
td->td_retval[0] = p2->p_pid;
td->td_retval[1] = 0;
}
return (error);
}
int
rfork(td, uap)
struct thread *td;
struct rfork_args *uap;
{
struct proc *p2;
int error;
/* Don't allow kernel-only flags. */
if ((uap->flags & RFKERNELONLY) != 0)
return (EINVAL);
AUDIT_ARG(fflags, uap->flags);
error = fork1(td, uap->flags, 0, &p2);
if (error == 0) {
td->td_retval[0] = p2 ? p2->p_pid : 0;
td->td_retval[1] = 0;
}
return (error);
}
int nprocs = 1; /* process 0 */
int lastpid = 0;
SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
"Last used PID");
/*
* Random component to lastpid generation. We mix in a random factor to make
* it a little harder to predict. We sanity check the modulus value to avoid
* doing it in critical paths. Don't let it be too small or we pointlessly
* waste randomness entropy, and don't let it be impossibly large. Using a
* modulus that is too big causes a LOT more process table scans and slows
* down fork processing as the pidchecked caching is defeated.
*/
static int randompid = 0;
static int
sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
{
int error, pid;
error = sysctl_wire_old_buffer(req, sizeof(int));
if (error != 0)
return(error);
sx_xlock(&allproc_lock);
pid = randompid;
error = sysctl_handle_int(oidp, &pid, 0, req);
if (error == 0 && req->newptr != NULL) {
if (pid < 0 || pid > PID_MAX - 100) /* out of range */
pid = PID_MAX - 100;
else if (pid < 2) /* NOP */
pid = 0;
else if (pid < 100) /* Make it reasonable */
pid = 100;
randompid = pid;
}
sx_xunlock(&allproc_lock);
return (error);
}
SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
int
fork1(td, flags, pages, procp)
struct thread *td;
int flags;
int pages;
struct proc **procp;
{
struct proc *p1, *p2, *pptr;
struct proc *newproc;
int ok, trypid;
static int curfail, pidchecked = 0;
static struct timeval lastfail;
struct filedesc *fd;
struct filedesc_to_leader *fdtol;
struct thread *td2;
struct sigacts *newsigacts;
struct vmspace *vm2;
int error;
/* Can't copy and clear. */
if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
return (EINVAL);
p1 = td->td_proc;
/*
* Here we don't create a new process, but we divorce
* certain parts of a process from itself.
*/
if ((flags & RFPROC) == 0) {
if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
(flags & (RFCFDG | RFFDG))) {
PROC_LOCK(p1);
if (thread_single(SINGLE_BOUNDARY)) {
PROC_UNLOCK(p1);
return (ERESTART);
}
PROC_UNLOCK(p1);
}
error = vm_forkproc(td, NULL, NULL, NULL, flags);
if (error)
goto norfproc_fail;
/*
* Close all file descriptors.
*/
if (flags & RFCFDG) {
struct filedesc *fdtmp;
fdtmp = fdinit(td->td_proc->p_fd);
fdfree(td);
p1->p_fd = fdtmp;
}
/*
* Unshare file descriptors (from parent).
*/
if (flags & RFFDG)
fdunshare(p1, td);
norfproc_fail:
if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
(flags & (RFCFDG | RFFDG))) {
PROC_LOCK(p1);
thread_single_end();
PROC_UNLOCK(p1);
}
*procp = NULL;
return (error);
}
/*
* XXX
* We did have single-threading code here
* however it proved un-needed and caused problems
*/
vm2 = NULL;
/* Allocate new proc. */
newproc = uma_zalloc(proc_zone, M_WAITOK);
if (TAILQ_EMPTY(&newproc->p_threads)) {
td2 = thread_alloc();
if (td2 == NULL) {
error = ENOMEM;
goto fail1;
}
proc_linkup(newproc, td2);
} else
td2 = FIRST_THREAD_IN_PROC(newproc);
/* Allocate and switch to an alternate kstack if specified. */
if (pages != 0) {
if (!vm_thread_new_altkstack(td2, pages)) {
error = ENOMEM;
goto fail1;
}
}
if ((flags & RFMEM) == 0) {
vm2 = vmspace_fork(p1->p_vmspace);
if (vm2 == NULL) {
error = ENOMEM;
goto fail1;
}
}
#ifdef MAC
mac_proc_init(newproc);
#endif
knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx);
STAILQ_INIT(&newproc->p_ktr);
/* We have to lock the process tree while we look for a pid. */
sx_slock(&proctree_lock);
/*
* Although process entries are dynamically created, we still keep
* a global limit on the maximum number we will create. Don't allow
* a nonprivileged user to use the last ten processes; don't let root
* exceed the limit. The variable nprocs is the current number of
* processes, maxproc is the limit.
*/
sx_xlock(&allproc_lock);
if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred,
PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) {
error = EAGAIN;
goto fail;
}
/*
* Increment the count of procs running with this uid. Don't allow
* a nonprivileged user to exceed their current limit.
*
* XXXRW: Can we avoid privilege here if it's not needed?
*/
error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
if (error == 0)
ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
else {
PROC_LOCK(p1);
ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
lim_cur(p1, RLIMIT_NPROC));
PROC_UNLOCK(p1);
}
if (!ok) {
error = EAGAIN;
goto fail;
}
/*
* Increment the nprocs resource before blocking can occur. There
* are hard-limits as to the number of processes that can run.
*/
nprocs++;
#ifdef VIMAGE
P_TO_VPROCG(p1)->nprocs++;
#endif
/*
* Find an unused process ID. We remember a range of unused IDs
* ready to use (from lastpid+1 through pidchecked-1).
*
* If RFHIGHPID is set (used during system boot), do not allocate
* low-numbered pids.
*/
trypid = lastpid + 1;
if (flags & RFHIGHPID) {
if (trypid < 10)
trypid = 10;
} else {
if (randompid)
trypid += arc4random() % randompid;
}
retry:
/*
* If the process ID prototype has wrapped around,
* restart somewhat above 0, as the low-numbered procs
* tend to include daemons that don't exit.
*/
if (trypid >= PID_MAX) {
trypid = trypid % PID_MAX;
if (trypid < 100)
trypid += 100;
pidchecked = 0;
}
if (trypid >= pidchecked) {
int doingzomb = 0;
pidchecked = PID_MAX;
/*
* Scan the active and zombie procs to check whether this pid
* is in use. Remember the lowest pid that's greater
* than trypid, so we can avoid checking for a while.
*/
p2 = LIST_FIRST(&allproc);
again:
for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) {
while (p2->p_pid == trypid ||
(p2->p_pgrp != NULL &&
(p2->p_pgrp->pg_id == trypid ||
(p2->p_session != NULL &&
p2->p_session->s_sid == trypid)))) {
trypid++;
if (trypid >= pidchecked)
goto retry;
}
if (p2->p_pid > trypid && pidchecked > p2->p_pid)
pidchecked = p2->p_pid;
if (p2->p_pgrp != NULL) {
if (p2->p_pgrp->pg_id > trypid &&
pidchecked > p2->p_pgrp->pg_id)
pidchecked = p2->p_pgrp->pg_id;
if (p2->p_session != NULL &&
p2->p_session->s_sid > trypid &&
pidchecked > p2->p_session->s_sid)
pidchecked = p2->p_session->s_sid;
}
}
if (!doingzomb) {
doingzomb = 1;
p2 = LIST_FIRST(&zombproc);
goto again;
}
}
sx_sunlock(&proctree_lock);
/*
* RFHIGHPID does not mess with the lastpid counter during boot.
*/
if (flags & RFHIGHPID)
pidchecked = 0;
else
lastpid = trypid;
p2 = newproc;
p2->p_state = PRS_NEW; /* protect against others */
p2->p_pid = trypid;
/*
* Allow the scheduler to initialize the child.
*/
thread_lock(td);
sched_fork(td, td2);
thread_unlock(td);
AUDIT_ARG(pid, p2->p_pid);
LIST_INSERT_HEAD(&allproc, p2, p_list);
LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
PROC_LOCK(p2);
PROC_LOCK(p1);
sx_xunlock(&allproc_lock);
bcopy(&p1->p_startcopy, &p2->p_startcopy,
__rangeof(struct proc, p_startcopy, p_endcopy));
pargs_hold(p2->p_args);
PROC_UNLOCK(p1);
bzero(&p2->p_startzero,
__rangeof(struct proc, p_startzero, p_endzero));
p2->p_ucred = crhold(td->td_ucred);
/* Tell the prison that we exist. */
prison_proc_hold(p2->p_ucred->cr_prison);
PROC_UNLOCK(p2);
/*
* Malloc things while we don't hold any locks.
*/
if (flags & RFSIGSHARE)
newsigacts = NULL;
else
newsigacts = sigacts_alloc();
/*
* Copy filedesc.
*/
if (flags & RFCFDG) {
fd = fdinit(p1->p_fd);
fdtol = NULL;
} else if (flags & RFFDG) {
fd = fdcopy(p1->p_fd);
fdtol = NULL;
} else {
fd = fdshare(p1->p_fd);
if (p1->p_fdtol == NULL)
p1->p_fdtol =
filedesc_to_leader_alloc(NULL,
NULL,
p1->p_leader);
if ((flags & RFTHREAD) != 0) {
/*
* Shared file descriptor table and
* shared process leaders.
*/
fdtol = p1->p_fdtol;
FILEDESC_XLOCK(p1->p_fd);
fdtol->fdl_refcount++;
FILEDESC_XUNLOCK(p1->p_fd);
} else {
/*
* Shared file descriptor table, and
* different process leaders
*/
fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
p1->p_fd,
p2);
}
}
/*
* Make a proc table entry for the new process.
* Start by zeroing the section of proc that is zero-initialized,
* then copy the section that is copied directly from the parent.
*/
PROC_LOCK(p2);
PROC_LOCK(p1);
bzero(&td2->td_startzero,
__rangeof(struct thread, td_startzero, td_endzero));
bcopy(&td->td_startcopy, &td2->td_startcopy,
__rangeof(struct thread, td_startcopy, td_endcopy));
bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
td2->td_sigstk = td->td_sigstk;
td2->td_sigmask = td->td_sigmask;
td2->td_flags = TDF_INMEM;
#ifdef VIMAGE
td2->td_vnet = NULL;
td2->td_vnet_lpush = NULL;
#endif
/*
* Duplicate sub-structures as needed.
* Increase reference counts on shared objects.
*/
p2->p_flag = P_INMEM;
p2->p_swtick = ticks;
if (p1->p_flag & P_PROFIL)
startprofclock(p2);
td2->td_ucred = crhold(p2->p_ucred);
if (flags & RFSIGSHARE) {
p2->p_sigacts = sigacts_hold(p1->p_sigacts);
} else {
sigacts_copy(newsigacts, p1->p_sigacts);
p2->p_sigacts = newsigacts;
}
if (flags & RFLINUXTHPN)
p2->p_sigparent = SIGUSR1;
else
p2->p_sigparent = SIGCHLD;
p2->p_textvp = p1->p_textvp;
p2->p_fd = fd;
p2->p_fdtol = fdtol;
/*
* p_limit is copy-on-write. Bump its refcount.
*/
lim_fork(p1, p2);
pstats_fork(p1->p_stats, p2->p_stats);
PROC_UNLOCK(p1);
PROC_UNLOCK(p2);
/* Bump references to the text vnode (for procfs) */
if (p2->p_textvp)
vref(p2->p_textvp);
/*
* Set up linkage for kernel based threading.
*/
if ((flags & RFTHREAD) != 0) {
mtx_lock(&ppeers_lock);
p2->p_peers = p1->p_peers;
p1->p_peers = p2;
p2->p_leader = p1->p_leader;
mtx_unlock(&ppeers_lock);
PROC_LOCK(p1->p_leader);
if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
PROC_UNLOCK(p1->p_leader);
/*
* The task leader is exiting, so process p1 is
* going to be killed shortly. Since p1 obviously
* isn't dead yet, we know that the leader is either
* sending SIGKILL's to all the processes in this
* task or is sleeping waiting for all the peers to
* exit. We let p1 complete the fork, but we need
* to go ahead and kill the new process p2 since
* the task leader may not get a chance to send
* SIGKILL to it. We leave it on the list so that
* the task leader will wait for this new process
* to commit suicide.
*/
PROC_LOCK(p2);
psignal(p2, SIGKILL);
PROC_UNLOCK(p2);
} else
PROC_UNLOCK(p1->p_leader);
} else {
p2->p_peers = NULL;
p2->p_leader = p2;
}
sx_xlock(&proctree_lock);
PGRP_LOCK(p1->p_pgrp);
PROC_LOCK(p2);
PROC_LOCK(p1);
/*
* Preserve some more flags in subprocess. P_PROFIL has already
* been preserved.
*/
p2->p_flag |= p1->p_flag & P_SUGID;
td2->td_pflags |= td->td_pflags & TDP_ALTSTACK;
SESS_LOCK(p1->p_session);
if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
p2->p_flag |= P_CONTROLT;
SESS_UNLOCK(p1->p_session);
if (flags & RFPPWAIT)
p2->p_flag |= P_PPWAIT;
p2->p_pgrp = p1->p_pgrp;
LIST_INSERT_AFTER(p1, p2, p_pglist);
PGRP_UNLOCK(p1->p_pgrp);
LIST_INIT(&p2->p_children);
callout_init(&p2->p_itcallout, CALLOUT_MPSAFE);
#ifdef KTRACE
/*
* Copy traceflag and tracefile if enabled.
*/
mtx_lock(&ktrace_mtx);
KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode"));
if (p1->p_traceflag & KTRFAC_INHERIT) {
p2->p_traceflag = p1->p_traceflag;
if ((p2->p_tracevp = p1->p_tracevp) != NULL) {
VREF(p2->p_tracevp);
KASSERT(p1->p_tracecred != NULL,
("ktrace vnode with no cred"));
p2->p_tracecred = crhold(p1->p_tracecred);
}
}
mtx_unlock(&ktrace_mtx);
#endif
/*
* If PF_FORK is set, the child process inherits the
* procfs ioctl flags from its parent.
*/
if (p1->p_pfsflags & PF_FORK) {
p2->p_stops = p1->p_stops;
p2->p_pfsflags = p1->p_pfsflags;
}
#ifdef KDTRACE_HOOKS
/*
* Tell the DTrace fasttrap provider about the new process
* if it has registered an interest.
*/
if (dtrace_fasttrap_fork)
dtrace_fasttrap_fork(p1, p2);
#endif
/*
* This begins the section where we must prevent the parent
* from being swapped.
*/
_PHOLD(p1);
PROC_UNLOCK(p1);
/*
* Attach the new process to its parent.
*
* If RFNOWAIT is set, the newly created process becomes a child
* of init. This effectively disassociates the child from the
* parent.
*/
if (flags & RFNOWAIT)
pptr = initproc;
else
pptr = p1;
p2->p_pptr = pptr;
LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
sx_xunlock(&proctree_lock);
/* Inform accounting that we have forked. */
p2->p_acflag = AFORK;
PROC_UNLOCK(p2);
/*
* Finish creating the child process. It will return via a different
* execution path later. (ie: directly into user mode)
*/
vm_forkproc(td, p2, td2, vm2, flags);
if (flags == (RFFDG | RFPROC)) {
PCPU_INC(cnt.v_forks);
PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize +
p2->p_vmspace->vm_ssize);
} else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
PCPU_INC(cnt.v_vforks);
PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize +
p2->p_vmspace->vm_ssize);
} else if (p1 == &proc0) {
PCPU_INC(cnt.v_kthreads);
PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize +
p2->p_vmspace->vm_ssize);
} else {
PCPU_INC(cnt.v_rforks);
PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize +
p2->p_vmspace->vm_ssize);
}
/*
* Both processes are set up, now check if any loadable modules want
* to adjust anything.
* What if they have an error? XXX
*/
EVENTHANDLER_INVOKE(process_fork, p1, p2, flags);
/*
* Set the child start time and mark the process as being complete.
*/
microuptime(&p2->p_stats->p_start);
PROC_SLOCK(p2);
p2->p_state = PRS_NORMAL;
PROC_SUNLOCK(p2);
/*
* If RFSTOPPED not requested, make child runnable and add to
* run queue.
*/
if ((flags & RFSTOPPED) == 0) {
thread_lock(td2);
TD_SET_CAN_RUN(td2);
sched_add(td2, SRQ_BORING);
thread_unlock(td2);
}
/*
* Now can be swapped.
*/
PROC_LOCK(p1);
_PRELE(p1);
PROC_UNLOCK(p1);
/*
* Tell any interested parties about the new process.
*/
knote_fork(&p1->p_klist, p2->p_pid);
SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0);
/*
* Preserve synchronization semantics of vfork. If waiting for
* child to exec or exit, set P_PPWAIT on child, and sleep on our
* proc (in case of exit).
*/
PROC_LOCK(p2);
while (p2->p_flag & P_PPWAIT)
cv_wait(&p2->p_pwait, &p2->p_mtx);
PROC_UNLOCK(p2);
/*
* Return child proc pointer to parent.
*/
*procp = p2;
return (0);
fail:
sx_sunlock(&proctree_lock);
if (ppsratecheck(&lastfail, &curfail, 1))
printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n",
td->td_ucred->cr_ruid);
sx_xunlock(&allproc_lock);
#ifdef MAC
mac_proc_destroy(newproc);
#endif
fail1:
if (vm2 != NULL)
vmspace_free(vm2);
uma_zfree(proc_zone, newproc);
pause("fork", hz / 2);
return (error);
}
/*
* Handle the return of a child process from fork1(). This function
* is called from the MD fork_trampoline() entry point.
*/
void
fork_exit(callout, arg, frame)
void (*callout)(void *, struct trapframe *);
void *arg;
struct trapframe *frame;
{
struct proc *p;
struct thread *td;
struct thread *dtd;
td = curthread;
p = td->td_proc;
KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
td, td->td_sched, p->p_pid, td->td_name);
sched_fork_exit(td);
/*
* Processes normally resume in mi_switch() after being
* cpu_switch()'ed to, but when children start up they arrive here
* instead, so we must do much the same things as mi_switch() would.
*/
if ((dtd = PCPU_GET(deadthread))) {
PCPU_SET(deadthread, NULL);
thread_stash(dtd);
}
thread_unlock(td);
/*
* cpu_set_fork_handler intercepts this function call to
* have this call a non-return function to stay in kernel mode.
* initproc has its own fork handler, but it does return.
*/
KASSERT(callout != NULL, ("NULL callout in fork_exit"));
callout(arg, frame);
/*
* Check if a kernel thread misbehaved and returned from its main
* function.
*/
if (p->p_flag & P_KTHREAD) {
printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
td->td_name, p->p_pid);
kproc_exit(0);
}
mtx_assert(&Giant, MA_NOTOWNED);
EVENTHANDLER_INVOKE(schedtail, p);
}
/*
* Simplified back end of syscall(), used when returning from fork()
* directly into user mode. Giant is not held on entry, and must not
* be held on return. This function is passed in to fork_exit() as the
* first parameter and is called when returning to a new userland process.
*/
void
fork_return(td, frame)
struct thread *td;
struct trapframe *frame;
{
userret(td, frame);
#ifdef KTRACE
if (KTRPOINT(td, KTR_SYSRET))
ktrsysret(SYS_fork, 0, 0);
#endif
mtx_assert(&Giant, MA_NOTOWNED);
}